This application relates to operations and designs of devices that include a mirror engaged to a rotation actuator to rotate around one or more rotational axes.
A rotation actuator may be engaged to a mirror to control the orientation or rotation of that mirror. Various rotation actuators may be used for this purpose, including but not limited to, galvanometers, piezo-electric actuators, and MEMS actuators fabricated on semiconductor substrates. Such a rotation actuator generally includes a mechanism that produces a force or torque to move the mirror when energy applied thereto is turned on or changed.
A typical galvanometer, for example, has an electromagnetic assembly in which a coil carrying an electric current is placed inside a magnetic field to rotate around a rotational axis. The electromagnetic interaction between the magnetic field and the current produces a torque to cause the rotation of the coil. Springs may be movably engaged to and hence suspend the coil to a fixed frame to rotate around one or two axes. In one example where the magnetic field is a static field, the direction and magnitude of the current in the coil may be controlled to control the rotational motion of the coil. The coil rotation under the torque can deform the springs to cause a counter-acting mechanical torque generated by the torsion of the springs. When the current is set at a particular magnitude in a selected direction, the coil can be set at a stationary state at a respective rotational angle when the torque on the coil is equal to the counter-acting torque on the coil. The current can be adjusted to change the torque on the coil and hence the orientation of the coil.